This invention relates generally to hermetically sealed refrigeration compressors and, more particularly, to oil-stirring devices for use in such compressors.
The hermetically sealed refrigeration compressor is almost universally used in household refrigerators and freezers, as well as room air conditioners and many other machines using a refrigeration system, such as ice-making machines, vending machines, and the like. In these compressors, there is an oil reservoir in the bottom portion of the sealed container, while the upper space is filled with the refrigerant gas so that the entire internal system, in combination with the evaporator and condenser coil assemblies, is completely sealed from the outside air. Once the system is charged with a refrigerant, it continues to operate as a sealed unit and the oil in the reservoir at the bottom of the container must last for a long period of time to lubricate the moving parts of the compressor without interfering with the rest of the refrigerant-containing system.
One of the problems with refrigeration compressors, particularly when they are used in household refrigerators and freezers, is that of the noise produced by the mechanism. While the noise has many sources within the compressors, it has been recognized that noise can be reduced by producing a controlled amount of foaming of the lubricating oil. While the earliest designs, such as those disclosed in U.S. Pat. Nos. 3,066,857 and 3,155,312, both assigned to the assignee of the present invention, use the approach of actually bubbling refrigerant through the lubricating oil, it was subsequently found that a simpler approach was to put a stirring device on the end of the motor crankshaft and have it immersed a short distance below the upper surface of the lubricating oil. While such stirring in itself would assist the foaming, it is also recognized that much of the foaming action results from the fact that a certain amount of the gaseous refrigerant dissolves in the lubricating oil and the agitating action aids in causing the gaseous refrigerant to effervesce and form small bubbles. This results in the formation of an oil foam on the upper surface of the oil and around the interior of the compressor shell.
Many devices have been proposed for producing this stirring action, including those shown in U.S. Pat. Nos. 3,147,914; 3,480,205 and 3,614,384. However, such devices tended to be rather delicate and easily damaged during the assembly of the compressor and if distorted in any way would produce an excessive amount of agitation, which could not only interfere with proper lubrication of the compressor but could also result in an increase in energy consumption because of the amount of work put into the agitating action.
An improved oil stirring device is shown in U.S. Pat. No. 4,127,994, also assigned to the assignee of the present invention, which utilizes a conical sheet metal member with perforations therein which is pressed into place on the end of the crankshaft and projects downwardly a distance into the oil. With this device, there was an improved reduction in noise, although the device tended to be expensive to manufacture and could be bent and distorted out of the proper conical shape during normal handling and during assembly of the compressor.